Distillation of fatty acids



p 9, 1952 E. A. LAWRENCE DISTILLATION OF FATTY ACIDS Filed Aug. 4, 1942? VACUUM T |IEFl sax/R05 26 3/ I a VACUUM q a w I (37 27 4a 49 50. //6 570mm TANK 52 J/ HlIEl'ZB- I I: i s I 1.12 i i I 1 i i l 1 I i 23 I i i I i INVENTOR.

1" EDWARD ALAWRENCE m I 1 BY Patented Sept. 9, 1952 UNITED STATES PATENT OFFICE DISTILLATION OF FATTY ACIDS Edward A. Lawrence, New York, 'N. Y., assignor to Colgate-Palmolive-Peet Company, Jersey City, N. J., a corporation ofDelaware Application August 4, 1949, Serial No. 108,531

(01. aze-c6) 6 Claims. 1 This invention relates to improvements in the art of distillation and the refining of liquids,

and more particularly to a method and apparatus for distilling high boiling liquids, particularly fatty acids.

Although the invention will be described as applied to the distillation of fatty. acids to .pro-

apparatus have been proposed for use in'the distillationof high boiling liquids, and certain of these have beenemployed with some degree of succes in the distillation of fatty acidsand the like material.

However, prior to this inyention, in so far as'known, no commercially practicable method and apparatushas been. devised for distilling fatty acids at a relatively high rate while effecting the substantially complete removal of the non-volatile impurities entrained in the vapors, whereby a fatty acid distillate which is practically free from coloring matter or of very light color is produced. The present invention provides such a method and apparatus for accomplishing these desired-results.

There are a number of factors known to adversely affect the quality of the distillate obtained by the distillation of fatty acids. Such factors include the use of high temperatures; the presence of atmospheric air; the prolonged heating of the fatty acid-material; and the presence of entrained impurities in the vapors leaving the vaporizer or still which if not satisfactorily removed result in the'production'of a dark colored distillate. In order to lessen the deleterious effects caused by the use of relatively high temperatures and protracted heating of the fatty acid material and to prevent the material from being exposed to air at such elevated temperatures it has been the practice, ingeneral, to

carry out the distillation under subatmospheric pressure conditions. Also, it has been common to introduceste'amat low absolute pressure into the system to lower the effective temperature at which the distillation maybe carried out, and

to'assist in preventing air from contacting the heated fatty acid material, thus avoiding its harmful influence. fljlash distillation methods likewise have been-employed wherein the fatty acid material is heate d to high temperatures in an enclosed pip for a shortjtime to store up in theliquidenough heat to convert it into 'avapor immediately upon relieving the *pressure on the heated liquid material, for'eiiample, as'by' sprayiii) '2 ing the heated material into. a low pressure chamber. While this treatment avoids somelof undesirable effects produced when the fatty acid material is heated at lower temperaturesfor long'periods of time, the high temperatures and pressures to which the fatty acid material is subjected, even for short periods of time/tendlto cause more or less polymerization, craoking a'nfd the formation of awcertain amount of tar-like residues whichisundesirable.

along in the vapor stream to the condenser a darker colored distillate results than otherwise would be the case. Such color-bearing impurities comprising unvolatilized liquid particles are unavoidably projected into the upwardly moving vapor stream as the fatty acid material distills and becomes entrained in the vapors Various devices and methods have been employed in attempts to separate the entrainment from the vapors before the same are condensed. In general, such devices and methods have involved more or less abrupt changes in thedirectional movement of the vapors for the purpose of throwing entrained material out of the vapor stream. Use has been made, for example, of cyclone separators, baffles, spiral ,ribs, multiple concentrically arranged walls or cones positioned in the path of the vapor stream to present a tortuous path for the vapor to travel so that entrained particles are caused to separate from the vapor beforethe same is condensed. These devices have not 'proven entirely satisfactory principally because toobtain the best results a high resistance to the vapor flow is required, which increase in resistance produces a high pressure drop in the system with accompanying 'low optimum feed rate. Furthermore, althrough such high resistance'to vapor fiow'is effective for removing the bulk of the entrained particles, it has not been found to be particularly effective in bringing about the separation of the small "percentage (usually from one 'to three per cent) of undistilled or undistillable relatively minute liquid particles which are held insuspension and widely dispersed in the rising vapors. In the distillation of higher fatty acids, the acid vapor is impure because of such entrainment and, "as aforementioned, if this entrained material is not removed, or at least substantially reduced in concentration, the distillate producedtherefromwill be of inferior color and quality.

It has now been discovered that a very satisfactory and highly eflicacious method'of' removing entrainment from fatty vapors, without interfering with the vapor flow to any great extent, comprises distilling such fatty acid material and passing the resulting fatty acid vapors formed into a zone wherein the vapors are caused to at course, vary somewhat with different fatty acids or fatty acid mixtures, being a function not only .of the temperature, conversion factor and gas constant per mole, but also the molecular weight, varying inversely with respect to the square root of such molecular weight. In the distillation of crude fatty acids, for example, red oil, tallow acids, coconut oil acids, and the like commercial fatty acids, the improved results are obtained in accordance with this invention When the velocity of the fatty acid vapors are made to reach or approximate the maximum or acoustic velocity at the entrance to the separator. For split tallow fatty acids, such for example obtained by counter current hydrolysis in known manner, the acoustic velocity under the condition maintained Was on the order of 400 to 450 ft./sec. In the case of coconut oil fatty acids which comprise lower molecular weight acids the acoustic velocity under the conditions imposed was on the order of '480'to 500 ft./ sec.

ing constructed and arranged in the system'so that under normal operating conditions of temperature and pressure the velocity of the vapor passing from the vaporizer to the separator will be increased substantially so that at the inlet to the separator it will at least approximate the l acoustic velocity. The highest velocity will normally occur in the system at the lowest pressure point in the line having the smallest cross-sectional area, and accordingly the fatty acid vapor may be made to flow at the acoustic velocity as it enters the separator by enlarging the cross-sectional area of the outlet with respect to the area of the inlet to the separator, and operating the system under a sufficiently high vacuum so that the vapors will attain acoustic velocity at the separator inlet.

One or more centrifugal separator units may be used, such as illustrated in the drawings, and the improved results are obtained in accordance with this invention where the system is constructed and operated so as to provide acoustic velocity of the vapor at the inlet to at least one of the separators, and preferably, where two or more separators are employed, the last separator in the series and from which the purified vapors may be conducted to other processin apparatus for use as such, or may be passed to a condenser and recovered as distillate.

A significant advantage of the invention is that a the improvement in entraimnent removal is accomplished without creating a great resistance to the free passage of the vapors with accompanyfore it has not been possible to attain without 2% sacrifice in the efflciency of entrainment removal.

In order to provide a clearer understanding of the invention reference may be made to the drawings forming a part of this application wherein there is illustrated an apparatus embodying the principles of the invention and one manner in which the improved process may be carried out.

Fig. 1 illustrates more or less diagrammatically a distillation and entrainment removal system including a vaporizer and an acoustically operating separator which is constructed and operated in accordance with this invention, a part of the vaporizer being broken away to indicate the heating arrangement; I

Fig. 2 is a similar distillation system as shown in Fig. 1 wherein two centrifugal separators are employed, being connected in series with the last one arranged to operate at acoustic velocity at the separator inlet;

Fig. 3 is an enlarged vertical section through a separator embodying the novel features of the invention taken on the line 3-3 of Fig. 4 and looking in the direction of the arrows;

Fig. 4 is a similarly enlarged horizontal section view of the separator taken on the line 44 of Fig. 3 and looking in the direction of the arrows.

In Fig. 1 there is illustrated a distillation system wherein a single acoustically operating centrifugal separator is utilized to remove entrainment. In the system illustrated in Fig. 2, two centrifugal separators are used as generally preferred in commercial operation, the separators being connected in series with the second or last separator constructed so as to establish acoustic velocity of the vapor as the same enters the separator.

Referring to the drawings, the vacuum distillation system shown in Fig. 1 comprises an up-fiow vaporizer or still l5 into which the crude fatty acids to be distilled are introduced, as for example acids obtained by countercurrent hydrolysis, or from any other source, and which preferably are substantially free from dissolved and emulsified water. The crude acids are suitably accumulated in a storage receptacle l6, being withdrawn therefrom for transfer to the vaporizer [5 through the pipe line I! by means of pump [8 connected in line IT. From the pump the fatty acid material passes to a suitable heat exchanger I9 which preheats the fatty acids as they are fed to the vaporizer (5 through pipe line 20, the vaporizer being suitably heated as by means of hot diphenyl vapor introduced into the chamber 2|. Other suitable means for heating the vaporizer may be used such as steam, etc. The temperature of the fatty acid material in the vaporizer I5 is increased to about 250 C. by the heating fluid so that the acids are readily volatilized under the vacuum conditions employed. Acid vapors produced in the vaporizer pass upwardly through the neck 22 and connecting pipe 23 which is connected to the acoustical separator 24, the pipe 23 being arranged to introduce the vapors tangentially into the lower part of the separator through inlet 25. Figs. 3 and 4 show in more detail the construction of the acoustical centrifugal separator and wherein the outlet 26 is made larger than the inlet 25 to cause the velocity of the vapors to be increased. so as to reach the acoustic velocity at the inlet to the separator.

The entrainment thrown out of the vapor stream in separator 24 is collected in the bottom part of the separator and may be removed through a suitable outlet line as indicatcd at 21 while the purified" vaporsspass upwardly andare discharged -through the enlarged outletopening Vapors =-so-discharged=- from the separator 24-are carried throughduct 28 tol'the condenser il-which is,'=in 1 turn; connected to 'a vacuum creating. means (not shown). "iThe-condenser; 2 9 ris-operated ata tem- "perature-low: enough 'to bring: about condensation :of'the volatilizedl fatty acids butis not so low as 'toi cause-solidification of the -fatty aoid distillate. Generallyra temperature ofabout 50 Cxis mainthrough duct -49 -'-tothe i primary condenser 50 whichin-communication with a vacuum. 'creatingmeans -notshown. i

Heat exchanger- 31- is i preferab1y--arranged to i preheat the fatty acidieedpas described -andcto a-functiom as' a surface condenser for fatty iacijd *yaporwhich will condense-- at --temperatures of about M G-180 C. The-primarycondenserfiflis operated at a-temperature: such asto cause =the uncondensed fatty acid -vapor discharged from-the -auxiliary condenser fl to be condensed to a liquid.

-tainedin the condenser by circulating-cooling water; Tor other suitable refrigerant, through the pipe line or coils as indicated at 30.. The fatty acid. distillate recovered in the condenser 3ll'may be suitably drawn off"through a distillate discharge line as diagrammatically illustrated at 3 I.

In the vacuum distillation system illustrated in Fig. 2, two centrifugal up-flow s'eparators 32 and 33 connected in series are used instead of a single separator, and the .sec'ond or-last separator 33 is constructed similar lto separator 24 in Fig. l to cause the vapors to reach acoustic velocity at the inlet thereto during operation. Referring to Fig. 2, the distillation system shown comprises a vaporizer 35, which-is constructed and heated in like manner as the vaporizer IS of-Fi'g. l. The crude fatty acid fedto the vaporizer through line 35 is arranged to ilow through the heat exchanger or auxiliary condenser 3'! and thence through line 38 to' the ivaporizer 35 During op- 'ibeing I conducted upwardly *and out tl irou-gh 'the -neck F3 9 a'nd connecting: pipe M1- to the centrifugal separato'r '32 ,the vapor entering tangentially iii-to r the bottom: portionl'of thes'ep'arator. Centrifugal i forcesiacting on the vapor as 'they1whirl upwardly i through the separatorw'li cause a large spor- 'tio'n of the heavier liquid entrained inthe vapor t01be thrown out- 0f the vapor stream,-lceing-collected in the bottom :portion of the *separator where the same =may be suitably -drawn on through a liquid discharge :line as indicatedat 42. The treated vapor then passes upwardly out of the separator 32 and isdischarged through the outlet 43 into the connecting pipe 44 which forms the-inlet to the acoustic velocity separator 33. The inlet pipe 44 -isarranged to introduce the vapors tangentiallyin'to the lower part -of the se'paratc'ir 33 similarly as in the case of separator Separator 33 is anacoustically operating separator as separator-24 (Fig. 1) whereby under the" vacuum conditions. of 1 operation the velocity of the vapor is madeto reach the acoustic value at its inlet 45. The entrainment thrown out of the'vapor stream in the acousticvseparator 33 is collected in the bottom Jpattiof the separator and lma'yibe drawn off through :a liquid'dischargeline as 'indic'ated at fieiwhileeth'e purified vaportpasses upw'ardly "land -is discharged 'thr'ough the "large outlet opening' fl. Vapor-sso discharged from the -sep'atator '33 'is conducted; to the heat exchairger -3lwthroligh a connecting .a pipe 48 and thence ;-'Lfhe' temperature "of the i condensing-surfaces for ta1-lowatty-aciddistillation is-preferably main- "-tai-ned at about a 50 -C., as by circulating"- cold watert-orthe-like' cooling flu-id, through suitable -coilswor. pipesas'indicated -atfi I 'The fa-tty acid distillate which collects in condensers 31 and =50 -may be suitably drawn off through distillate disch arge lines "52 which may be ioin'ed a-s diagrammatically illustrated in Fig. 2. 1

"Referring toi Figs. =3 and 4- wherein' -the: general construction of an 1 acoustical =ve1ocity separator, *such as employed in the fatty acid distillation systems shown (Fig. '1 and Fig. 2, separators24 and 33 respectively) the separator comprises a E'OYliI'ldllCflI-Shfill 55-having a central hollow drum which-is -closed atthe top by 'the cover '5'l' -a-nd arrangedi-n the bottom-section 58. *Altliough the r piarticular dimensions i of the separator mayqvary depending upomthe; capacity desired; in a' typical "-distillation system theoute'r diameter of thecentral --dr um 56 was approximately i one-third athemner diameter of R the separator and ofa 'length equal :to about three times the diameterw-of the inlet '25 as measured from a center line passing through the central axis of the inlet pipe-13, the

' :drumbeing accurately positioned so as tow-provide inlet is'approximately-one=thirdzthe iriside-diamete'r of the. separator or'she1l- 55. :Further', while the preferred construct inn of vthe separator includes the central drum :member 56, the same may be 'omitted as not being essential to the attainment of acoustic velocityof thevaporat "the inlet to the 'separater.

To c'ause the-vapor to attain acoustic 'velocityat the inlet '25 (Figs. 3 and l) of -the separaton-the outlet 26 is madesufiiciently larger in-cross-sectional area than i the inlet 25 'to causes. low pres- =sure..point to be-established at the inlet tothe separator during operation rather than at-some dther point in the'system. The cross-sectional area of the outlet and inlet of the acoustical velocity separator in any given case will depend 'upon the size Or capacity of the separator and material being treated. The size of the outlet may be made as large as economically feasible inasmuch as there isno cri-tical maximum size. In a typical distillation run wherein split tallow fatty acids were distilled in accordance with this invention and wherein an =acoustical cyclone type separatorwas used to treat the fatty acid vapor prior to condensing as described herein,

seq.

constant cross-section). Y

rate of the vapor is increased while the cross- 7 In the design of a system, such as that described and illustrated in the drawings, knowing the desired mass flow rate of vapor through the system and the pressure obtainable by the vacuum source,

the resistance to flow caused by the condensers I such as to keep the pressure drop in these parts low. This will require lines having large crosssectional areas relative to that which will be used upstream of the separator. Changes in pressure with the use of any particular system and equipment size may be determined using the method described by C. E. Lapple in Amer. Instfof Chemical Engineers, vol. 39 (1943), page 385 et The resistance to flow caused by the body of the separator and corresponding total pressure drop through the separator has been found experimentally to be quite low and for most purposes may be neglected. Referring to the pressure in the acoustical separator by the term 213 and the pressure in the inlet pipe, as

at 23 (Fig. 3) by the term in the cross-sectional area of the inlet 25 which will establish acoustic velocity at the inlet at a specified mass flow rate -may be calculated. In order to cause the linear velocity of the vapor to reach acoustic at the inlet 25 of the separator the value of pa (pressure at the inlet point 25) must be equal to I10 (representing the critical pressure and corresponding to the maximum mass discharge rate for a pipe of Where the mass flow sectional area at the inlet point 25 is held constant, the linear velocity of the vapor at that point will remain constant at the velocity of sound, 102 will remain equal to De but will also rise while 133' and all pressures downstream of this point will be relatively unaffected since the size of the equipment and capacity for handling the vapor from the acoustical separator as described will be much larger than that upstream of the separator, and the pressure drop-"Will be low. If on the other hand the mass flow rate is reduced below the value required to produce acoustic velocity at a particular size inlet as calculated then, of course, the linear velocity will fall below the acoustic value. I

The acoustic velocity of a vapor mass for adiabatic flow can be expressed by the following equation as set out by Lapple in the publication supra.

C =kgcpcvc (1) which for an ideal gas can be expressed as RT 2 g 2 C w where C=acoustic velocity, ft./sec.

'k= rat io of specific heats, dimensionless=c /cv 1b. mass. ft. lb. force, sec.

g =conversion factor 32.17

"T=ab solute temperature of fluid, F. absolute:

Rankine M w=molecular weight of fluid, lb. mass/lb. mole;

8 subscript c conditions at end of pipe corresponding to conditions of maximum mass flow.

For gases at very low pressures, the ideal gas law holds quite well so that the acoustic velocity (C) can be determined. The ratio of specific heats (k) is low for fatty acids and if the fiow is isothermal this term drops out regardless of its value. To illustrate the order of magnitude of the acoustic velocity for say tallow fatty acids (taking the average molecular weight for the fatty acids as equal to 274) and wherein conditions for Equation 2 are assumed, then (C) the acoustic velocity may be calcutaled as follows:

where V 7 RT 2 C kg assuming k==1 and T =942 Rankine Then ' 1546x942 2: C (32.17) X 2745 l70, 986

C=413.5 ft./sec.

In operating the distillation system as herein illustrated and described, the crude fatty acid material is fed to the vaporizer at such a rateas to produce a light-colored fatty acid distillate. The feed rate, however, must not be so low that acoustic velocity at the separator cannot be produced in accordance with the invention. Fur ther, where two or more centrifugal separators are employed it is preferable to make one in the series, and preferably the last one, operate at acoustic velocity at its inlet, however, if desired more than one of the separators may be designed to operate at acoustic inlet velocities.

The following table shows the results of a number of distillation runs made using Twitchell split #4 tallow'fatty acids (having a color of about 14 red and yellow as measured on a 4 inch Lovibond scale), and using a system such as illustrated in Fig. 1, the separator having two-inch diameter inlet and a six-inch diameter outlet, which outlet was approximately equal to the inner diameter of the separator, the central drum having a diameter of two inches and a length of approximately seven inches. The system was operated under a vacuum of approximately 30 mm. Hg absolute pressure at the vaporizer outlet:

In the. above table the velocity values were calculated from measured pressures and the acoustic velocity thus foundwas on the order of 400 to 450 ft./sec. Where the velocity of the vapor'at the inlet to the separator was decreased so that it fell substantially below the acoustic value it was observed that the color of the distillate became too dark to evaluate on 5%" Loviact-dim bond cell indicatingth -efliciency of entrainmentcremoval .lwasrloweredr; 1

Similar runs (4 to 11) Were-made with #4 tallow split fatty acids using two centrifugal separators connected-inseries as "in the system illustrated in Fig. 2. In:,runs, 4 through? the separators, employed.weraofthesame pati fi thel acoustically .operatingseparator usedinzpamiin'g... out. runs 1. to.-3 .exceptthat tin; thi ins anc the inlet and outlet of the separators were of equal oross-sectionalarea, each having a diameter; of two, inchest, In. runs fi .-.through 11, howeyer the second-separat rwa ,I modified,,by increasingthe diameter of th outlet from..two inches to six inches ,Whilegeta ingthediameter of, the;, inlet at twotinches s hat ,acoustic,..,.ve locity would .;be attained at the. nlet, tq=the sec: 11d se arator-i. Accord ngl ar n rshfl h rv oc yyo ithevapo atvi he nlet, to the senaratorsgwagbelow. acoustic whereas in; the case of runs 8 through ll the,-velocity.,of,,t e vapor was. nade to reachtthe.acoustic value. a theinlet' toethesecon r separator Th esults obtained are shown-in the foll wing table;

. Ta bZeJ L.

Velocity of yapor at e are ors Run Feed p Color ofdistillate No. Rate Lovibond C811 m/hr- Inlet #1 Inlet #2 Outlet #2 ft./sec fir/sec.

59 97 169 336 13R70Y. 141 112 176 389 Too dark to read. 105 106 178 410 Do.

72 113 182 294 17R70Y. 73 164 acoustic. 63 3.0R-30Y. 104 166 110"... 48 3.2R-30Y. 140 156 do 111 2.9R-29Y. 143 172 d0 103 3.3R-35Y.

As will be observed from the data of Table II the most efficient separation was effected utilizing the centrifugal separating system wherein critical or acoustic velocities of the fatty acid vapor were attained at the inlet to the second separator.

It has further been observed that operating the system so that the fatty acid vapor reaches acoustic velocity at the inlet to the centrifugal separator the system is relatively insensitive to changes in feed rate. For example, no appreciable variation in the efficiency of entrainment removal, as shown by the change in color of the distillate, is observed as the result of varying the feed rate over a range of about 75 to 200 lbs/hr. Sensitivity to changes in feed rate has been one of the disadvantages encountered heretofore in distillation systems.

In the foregoing runs Twitchell split tallow (#4 grade) acids were used since variations in the amount of entrainment present gave a much more noticeable change in the color of the resultant distillate. Similar runs made using a commercially distilled grade of red oil gavera distillate of lighter color and indicated that the improved results of the invention maybe obtained with different substances when the vapors are treated as described. The acoustical separator of the invention may be used with difierent vaporizers, stills or the like and in systems operating under different pressure and temperature conditions. A distillation apparatus, such as for example disclosed in the patent to Ittner 2,202,007, may be used if desired instead of the vaporizer herein illustrated and described' 3 i Centrirugal force, ot course, has long ibeenftlfiii ployed to separatesubstancesmf 'difierent densities; and more recently multiple stage centrifugal separator units have been proposed fort use :in purifyingpetroleumtvapor fractions In' so -far asknown, I however, no one heretofore has do vised a distillation system wherein-the vapon is purified ibyta methodin accordance with this-in vention whichal comprises (a) increasing the velocity of the. vapor until it: reaches acoustid velocity-then (bwsubjecting it to: centrifugal-ac tion to.: :causesubstantially completetseparation.

of .entrained-rnateriala Although it is-preterred to: employ in: the dis ti-llation system one-or -more-up fiow cyclone-type separators havinga-centralcdrum-or column with a vapor discharge outlet:arranged at'the topfdf the separator, the distillationsystem-may be operated using down-flow centrifugaltype A sepa rators when-arranged -andoperated so thatthe acoustic velocity of i the vapors is attained at th'e separator-inlet.

Whilea-particular-distillation system and sepa; rater means has. been shown and des crib'ed, t will beunderstoodthatthe process -of the in vention is:not-toberestricted to any one structure but that other apparatus within' thelscope of the disclosure- --and-,claims maybe employed in practicing the invention. It will also be understood that the process is capable of being carried out with suitable modifications, for example with or without preheating of the feed stock to the still. Further, the process may be carried out under varying temperature and pressure conditions, and utilizing diiferent types of Vaporizers, condenser an? auxiliary equipment as heretofore pointed ou What is claimed is:

1. In the distillation of high boiling liquids under vacuum without substantial chemical change, a process comprising the steps of (a) vaporizing under vacuum said liquid, (b) moving the vapoized mass under vacuum at a velocity substantially equal to the acoustic velocity, and (0) subjecting said acoustic velocity vapor to centrifugal action while maintaining said vapor under vacuum to cause separation of entrained material.

2. In the distillation of higher fatty acids without substantialdecomposition, a process which comprises the steps of distilling the fatty acid material under reduced pressure, passing the resulting vapor into a zone wherein said vapor under reduced pressure is caused to attain subtantially acoustic velocity, and subjecting said acoustic velocity vapor to a centrifugal purifying action while maintaining said fatty acid vapor under reduced pressure to cause the separation of entrainment from the vapor stream.

3. In the distillation of high boiling liquid without substantial chemical change, a process which comprises the steps of volatilizing the liquid under reduced pressure, passing the resulting vapor into a zone wherein said vapor under reduced pressure is caused to attain substantially acoustic velocity, thereafter subjecting the high velocity vapor to a centrifugal purifying action while maintaining said vapor under reduced pressure wherein said vapor moves along while twisting spirally about a central axis, and discharging the purified vapor along said axis without change in the direction of flow.

l. In the process of producing light colored fatty acids which comprises distilling said fatty purifying action to bring about the separation of ;:entrainment therefrom, the improvement which consists in causing said vapors while under-.1: reduced pressure to reach substantially acoustic, velocity just prior to subjection of the vapors to, saidv centrifugal purifying action while maintaining said fatty acids in the vapor state under reduced pressure.

The process of distilling fatty material Which, comprises heating the same under low absoluterpressure to volatilize a major portion of saidfatty material, moving said volatilized mass of fatty vapor, under low absolute pressure at acoustic velocity, and thereafter subjecting said vapor to a centrifugal purifying action while maintaining said vapor under low absolute pressure whereby said vapor is substantially freed of unvolatilized matter entrained therein.

6, A, process of treating a vapor stream of fatty material carrying entrained liquid particles to purify said vapor comprising moving the vapor. under reduced pressure at a velocity substantially equal to the acoustic value, and after said vapor is moving at acoustic velocity subjecting the same to a centrifugal purifying action while maintaining said vapor under reduced pressure to cause said entrained liquid particles to separate from ,the vapor stream.

EDWARD A. LAWRENCE.

12 REFERENCES CITED The following references are of record in the file of this patent: V

OTHER REFERENCES Lapple: Isothermal and Adiabatic Flow of Fluids, Transactions, American Institute of Chemical Engineers, vol. 39, pages 385-432, pages 404, 405, and 408-422 relied on, 1939.

Perry: Chemical Engineers Handbook, second edition, published 1941, by McGraw-Hill Book Co., New York, New York, pages 1857-1865.

Glinz: Impact Mills for the Manufacture of Powdered Coal, International Conference of Bituminous Coal, vol. II, pages 701-706.

I-Iirshfeld and Barnard: Elements of Heat Power Engineering," second edition,19l5 by Mo- Graw-I-Iill Book Co., New York, New York.

Stodola: Steam and Gas Turbines, published 1927 by McGraw-I-Iill Book Co., New York, New York, pages 43-48. 

6. A PROCESS OF TREATING A VAPOR STREAM OF FATTY MATERIAL CARRYING ENTRAINED LIQUID PARTICLES TO PURIFY SAID VAPOR COMPRISING MOVING THE VAPOR UNDER REDUCED PRESSURE AT A VELOCITY SUBSTANTIALLY EQUAL TO THE ACOUSTIC VALUE, AND AFTER SAID VAPOR IS MOVING AT ACOUSTIC VELOCITY SUBJECTING THE SAME TO A CENTRIFUGAL PURIFYING ACTION WHILE MAINTAINING SAID VAPOR UNDER REDUCED PRESSURE TO CAUSE SAID ENTRAINED LIQUID PARTICLES TO SEPARATE FROM THE VAPOR STREAM. 